Password
Have no idea what password ITunes is asking for when I want to restore my new IPhone 6S to the settings I had on my 6.
iPhone 6s, iOS 9.3
This sounds like its an encrypted iTunes Backup. At some point you, or someone with your iPhone, set up a local password on your computer in iTunes for your backups. The good news is that you have an indefinite number of tries. The bad news is, there is no way to reset the password. Here's a little more info on this subject: About encrypted backups in iTunes - Apple Support